The present invention relates to safety mechanisms for use in conjunction with pulleys mounted on a cable, wire or the like and more particularly to a safety mechanism for preventing disengagement of a pulley from a cable due to failure of a main support bolt in pulleys of the pivoting arm type.
Pulleys are typically used as the vehicle for suspending heavy objects from a cable, wire, rope or the like (hereinafter generically referred to as "cable") and allowing the suspended object to be moved along the length of the cable, e.g. by pulling the object or stringing the cable at an angle relative to horizontal. The cable itself is typically strung, at least at some point along its length, at an elevated height above the ground, and the necessity for insuring that the pulley will not fail in its ability to maintain a heavy object suspended on the cable is thus critically important.
Pulleys comprising a pair of bars with roller wheels sandwiched therebetween and having support arms which are pivotally connected to the bars have been used in the past and suffer from the fact that a single operative element such as a bolt which connects the arms and the bars is subject to failure because the bolt is the sole support element between the object and the cable and is repeatedly subjected to degradative friction by virtue of the pivoting of the arms on the bolts as well as torque and stress forces exerted by the weight of the suspended object on the main pivot bolt through the arms.
It is therefore an object of the invention to provide a safety mechanism in a pulley apparatus for preventing the pulley from becoming disengaged from a cable in the event of a failure in the primary support components of the pulley.